This invention relates to a method for treating textile and more particularly to a method for removing contaminants from textile.
In the textile processing industry, it is usual to process raw materials whose origin is not precisely known. Cotton and wool, for instance, are often purchased in the form of semimanufactured products which still contain various contaminants. In the case of cotton, those contaminants often consist of particles, such as sand and small plant remains, pigment particles and residues of plant protection agents and defoliants. In wool, the contaminants referred to can consist of soil or sand, or feces, urine, sweat, and greases (lanolin) originating from the animal from which the wool is derived.
As the textile processing industry often does not know of each batch of textile semimanufactured product which contaminants are present in it, the aim is to have processes available that are as universal as possible and by which different kinds of contaminants can be removed in a single step. In practice, for this reason, textile is normally treated with a composition comprising a polyacrylate.
A disadvantage of the known compositions based on polyacrylates is that polyacrylates are hardly, if at all, biodegradable. These substances are discharged along with the washing water used in the treatments. When the waste water is processed in a water purification plant, the polyacrylates end up in the sludge left, and thus end up in the environment.
It is an object of the invention to provide a method for treating textile, whereby contaminants are removed in an efficient manner and whereby the environment is not unacceptably burdened.
Surprisingly, it has now been found that the use of certain specific fructan polycarboxylic acids leads to a highly efficient, environment-friendly removal of contaminants from textile. Accordingly, the invention relates to a method for removing contaminants from textile, wherein the textile is treated with a fructan polycarboxylic acid which contains on average at least 0.05 carboxyl groups per monosaccharide unit.
It is of great advantage in a method according to the invention that the materials used are biodegradable. The fructan polycarboxylic acids used according to the invention have the property that they are broken down within a relatively short time to substances that are preferably water-soluble and non-toxic. The decomposition can occur inter alia by hydrolytic splitting, under the influence of light, air, water and/or microorganisms occurring in nature. Because of this property, the materials are designated by the term biodegradable materials.
In addition, it has been found that with the use of I the present fructan polycarboxylic acids, an attractive alternative to the conventionally used polyacrylates is also being offered as regards the effectiveness in the removal of contaminants.
As stated, according to the invention, textile is treated with a fructan polycarboxylic acid which contains on average at least 0.05 carboxyl groups per monosaccharide unit. Depending on the nature of the fructan polycarboxylic acid, the number of carboxyl groups per monosaccharide unit of the fructan polycarboxylic acid can be expressed in the total degree of substitution of carboxyl groups (DS) or the total degree of oxidation (DO). Preferably, the fructan polycarboxylic acid to be used contains between 0.5 and 3 carboxyl groups per monosaccharide unit. It will be clear that it is also possible according to the invention to use mixtures of different fructan polycarboxylic acids.
A fructan polycarboxylic acid is understood to mean any oligo- or polysaccharide that contains a plurality of anhydrofructan units and which has been converted into a polycarboxylic acid. The fructans on which a fructan polycarboxylic acid can be based can have a polydisperse chain length distribution and can have a linear or branched chain. Preferably, the fructans contain mainly xcex2-1,2 bonds, as in inulin, but they may also contain xcex2-2,6 bonds, as in levan. Suitable fructans can originate directly from a natural source, but may also have undergone a modification. Examples of modifications in this connection are reactions, known per se, which lead to a lengthening or shortening of the chain length. Suitable fructans have an average chain length (degree of polymerization, DP) of at least 2, up to about 1,000. Preferably, a fructan is used having a degree of polymerization of at least 3, more preferably at least 6, most preferably at least 10, up to about 60.
Fructans on which a fructan polycarboxylic acid can be based for use in a method according to the invention include, in addition to naturally occurring polysaccharides, industrially prepared polysaccharides, such as hydrolysis products, which have shortened chains, and fractionated products having a modified chain length, in particular a chain length of at least 10. A hydrolysis reaction for obtaining a fructan having a shorter chain length can be carried out enzymatically (for instance with endoinulinase), chemically (for instance with aqueous acid), physically (for instance thermally) or by the use of heterogeneous catalysis (for instance with an acid ion exchanger). Fractionation of fructans, such as inulin, can be accomplished, for instance, by crystallization at low temperature, separation with column chromatography, membrane filtration, and selective precipitation with an alcohol. Other fructans, such as fructans having a long chain, can be obtained, for instance, by crystallization, from fructans from which mono- and disaccharides have been removed, and fructans whose chain length has been enzymatically extended can also serve as a basis for a fructan polycarboxylic acid that is used in the present method. Further, reduced fructans can be used. These are fructans whose reducing terminal groups, normally fructose groups, have been reduced, for instance with sodium borohydride or hydrogen in the presence of a transition metal catalyst. Also eligible for use are fructans which have been chemically modified, such as crosslinked fructans and hydroxyalkylated fructans.